On Mon, 2003-10-27 at 10:15, Tarhon-Onu Victor wrote:
> select count(*) from items where channel <
> 5000; will never use any of the current indexes because none matches
> your WHERE clause (channel appears now only in multicolumn indexes).
No -- a multi-column index can be used to answer queries on a prefix of
the index's column list. So an index on (channel, xyz) can be used to
answer queries on (just) "channel".
-Neil
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
